This application is based upon U.S. Provisional Application Ser. No. 62/020,517 filed Jul. 3, 2014, the complete disclosure of which is hereby expressly incorporated by this reference.
Over time, culverts and sanitary sewer pipes deteriorate due to numerous factors. For example, corrugated metal pipes commonly used for culverts rust and buckle, and typically have a design life of 40-50 years. There are several options for replacement or repair of deteriorated pipes. One option is, pipe replacement, which requires digging, and in the case of under the road culverts, the road must be closed for excavation and laying of the new pipe. Another option is slip lining of the existing pipe, which often reduces the capacity by one-third or more. A third option is cured-in-place liners, which can be very costly in large diameters or non-round shapes.
A fourth option for repairing deteriorated culverts and sewer pipes is centrifugally cast concrete pipe (CCCP), which is economical and durable. U.S. Pat. No. 5,452,853 issued on Sep. 26, 1995 which is hereby expressly incorporated by this reference generally discloses the CCCP process. The centrifugally cast concrete pipe rehabilitation method applies thin layers of a coating such as structural grout, epoxy mortar, or polymer coating to produce a smooth, tightly bonded, water proofed finished product which does not significantly reduce the inner diameter of the pipe or culvert. Thus, after the repair the flow through the pipe or culvert is substantially the same as (or sometimes even better than) with the original pipe. This CCCP method is typically used on pipes having diameters between 30 inches to 120 inches, or larger.
The CCCP process begins with inspection of the pipe to be remediated to determine the thickness of the concrete to be applied inside the pipe, based on the depth, size, and shape of the pipe, depth of the local water table, water hydraulic pressure, and other factors. Then, flow through the pipe is stopped or diverted so that gravel, mud, roots and other debris can be removed from the pipe. The pipe interior is then scoured using a high pressure washer, and leaks and inverts are repaired, prior to concrete spin casting. The high speed concrete spin caster is then positioned in the pipe at the far end. The casting head moves through the pipe at a calculated speed to centrifugally cast a material evenly around the interior of the pipe to form a liner or coating. As used generally in the art, a “liner” is thicker than a “coating” and a “liner” is usually structural wherein a “coating” is protective but not structural. As used herein, however, the term “coating” includes both structural liners as well as non-structural protective coatings. The material used to form the coating may be a cementitious material, polymer, antibacterial agent, curing compound, or other suitable material or combination of materials. Regardless of the material used to form the coating, the resulting coating may be a thick structural layer or a thin protective layer. The spin caster can be stopped and started as needed, without joints or gaps. Depending on the desired thickness of the coating, multiple passes of the casting head may be required through the pipe to provide the desired strength. This coating can be applied to pipes made from any suitable material, including concrete, steel, plastic, corrugated metal pipe, and brick/mortar culverts. The coating cures or dries in place within a few hours, so that the culvert or sewer pipe can be quickly returned to service. The new coating water proofs, seals, and/or structurally reinforces the old pipe, and provides corrosion protection for sanitary and storm culverts or pipes, without trenching or digging, and at significant savings.
One downside to the CCCP process is the time that flow through the original pipe must be stopped or diverted during the application process. Since the casting equipment is moved through the pipe relatively slowly in the CCCP process, flow diversion is costly, particularly if multiple passes of the casting equipment through the pipe is required to achieve a desired thickness and/or strength of the coating.
Therefore, one objective of the present invention is the provision of an improved or modified centrifugally cast pipe liner process which minimizes flow diversion or stoppage time.
Another objective of the present invention is the provision of a CCCP process wherein the centrifugal casting is accomplished without diverting flow through the culvert or pipe.
A further objective of the present invention is the provision of a culvert and sewer pipe rehabilitation process which diverts water flow for a shorter time period than conventional CCCP processes.